Vitamin D is a fat-soluble vitamin, cyclopentane polyhydrophenanthrene. Vitamin D is a group of structurally related sterols. Its main function is to promote the absorption of calcium and phosphorus by small intestinal mucosa cells, thus preventing rickets, promoting skin cell growth, differentiation, and regulating immune function.
The main vitamin D types are D3 and D2. The former is made of 7- dehydrocholesterol under the skin by ultraviolet irradiation. The latter is made from an ergosterol found in plants or yeast that is exposed to ultraviolet light. Food sources of vitamin D include fatty sea fish, animal liver, egg yolks and cream.
Vitamin D deficiency can lead to rickets in children and osteomalacia in adults. Rickets occurs in infants and young children and is characterized by neuropsychiatric symptoms and skeletal changes. Neuropsychiatric symptoms include hyperhidrosis, night terrors, and irritability. Bone changes are related to age, growth rate and degree of vitamin D deficiency. May appear Lou osteomalacia, rib beading and so on. Osteomalacia occurs more often in adults, more common in pregnant women and frail elderly. The most common symptoms are bone pain, muscle weakness and bone tenderness.
The recommended daily intake for adults is 5μg. Pregnant and lactating women should double their intake.